The boss-latching system didn't become popular until fairly recently, like 3 years ago I would say. Eclipse started using it in 05 (although their spec is different than Empire, and the 05-06 Ego used a different size than the newer Eclipse markers) but the rise of a standardized accessory feedneck really helped to push it as of late. Empire released it back with the new Sniper and Resurrection Autococker, but the same system can be used with anybody's feedneck now which makes things easy.
I now make over 20 different adapters spread across the entire spectrum of marker threads and heights, and there's surely more to come. It's a pain to figure everything out but fortunately I've already done most of the legwork since I name each adapter with its height in inches which can be viewed right on the nummech website for instance this particular adapter is 0.625" tall overall. Easy for you or anybody to make more!